That’s one of the serious problems with any exceptionally high density energy storage technology. How do you keep the genie in the bottle, and protect the public from the critically stupid in our society.
There was a very cool design for a car whose power source was a high mass flywheel in a magnetic housing. You go to a power station, and the station would spin your flywheel up to some insane RPM rate. The possibility of using this in a hybrid vehicle meant you could get really excellent energy storage and return, it was very efficient.
The only drawback, was that if the bloody thing ever got out of containment, you had a death dealing juggernaut that would buzz-saw a swatch of destruction through the middle of wherever the now flying flywheel was pointed. Then some bright child imagined such a flywheel driven vehicle on a crowded freeway causing a chain reaction of thousands of other similar vehicle, and suddenly you pretty much have a scenario for mass destruction that looks like front row seats to Armageddon.
Whatever technology you finally pick, you’ll need to make it very safe, or decide it’s a Darwinian herd thinning tool.
There are several important fields for this type of energy storage. For automobiles, the system would be similar to that used in the Lockheed bus. However, a spinning flywheel gives rise to special torques, and a flywheel powered car going over the top of a hill might find itself flying like a ski jumper and landing at right angles to the road. To prevent such gyroscopic effects, two counter rotating flywheels on the same axis would add their stored energies, but their gyroscopic effects would cancel.